Method for changing the colour of a textile, fabric and garment

ABSTRACT

The invention refers to a fabric finishing method suitable for changing the colour of a coloured fabric thereby providing a vintage look to the fabric. The invention refers also to the fabric obtainable by the above method and to a garment comprising such fabric.

This application claims priority to and the benefit of EuropeanApplication No. 19173382.3 filed on May 8, 2019, the content of which isincorporated herein by reference in its entirety.

FIELD OF THE INVENTION

The present invention relates to the field of textile finishing, inparticular textile finishing to change colours in textiles to provide avintage look.

BACKGROUND OF THE INVENTION

Finishing processes for textiles are a group of heterogeneous processesthat modify the look, the performance and/or the “hand” (feel) of thefinished textiles or clothing.

Common finishing processes that modify the look of textiles, inparticular of denim, are those that deliberately remove the dyes inspecific areas of the textile (e.g. via mechanical abrasion orchemically) to provide a change in colour, and in particular a colourfading effect known as vintage look (also known as worn-out, washed orfaded look). Vintage look provides an “aged” effect to the textile thatis particularly sought out in denims for fashion reasons.

To obtain vintage look, physical and/or chemical processes such assanding, washing (stone, enzymes, or bleach washing) and lasertechnology have been used. Sanding, or sand blasting, is a mechanicalprocess in which localised abrasion is created. The process involvesblasting an abrasive material in powdered form at a very high speed andpressure. Sanding is known to be very hazardous for operating workers,and high health risks have been associated with sanding (e.g.silicosis). Washing processes involve a bath with various components,such as stones and/or chemicals, wherein the textile is immersed.Washing processes are wet processes and require great amounts of waterand stones/chemicals/enzymes that have to be correctly disposed. Forthis reasons, washing techniques are often harmful for the environmentand are not considered “green”. The most common washing techniques forproviding vintage look are stone, enzymes, and bleach washing.

Stone washing provides for stones, such as volcanic pumice stones, to beadded as abradants during textile washing. These stones scrape off dyeparticles from the surface of the yarn of the textile. Colour fading ismore apparent and less uniform with respect to other processes.Limitations of stone washing include wear, tear and damage of thetextile and eventual metal buttons and rivets thereof and damage of thewashing machines. Moreover, environmental harmful grit is produced bythe stones. Additionally, areas wherein the dye have to be removedcannot be selected when carrying out stone washing.

Enzyme washing can be used industrially for replacing or complementingthe stone washing process. In particular, enzymes such as laccases canbe used in processes related to decolourisation of indigo dyed textiles.Enzymes washing processes have the following limitations: limitedoperational conditions of the enzymes, requirement of post-treatment ofthe textile, and limited textile loading size of the washing machine.

Bleach washing is carried out with a strong oxidative bleaching agent,such as sodium hypochlorite or potassium permanganate. The bleachingeffect and decolouration usually depend on the strength of the bleachliquor, liquor quantity, temperature and treatment time. Parametersabove have to be carefully checked in every bleach washing process asfabric degradation can easily occur. This washing technique is the mostharmful washing process for operators and for the environment, as largequantities of harmful chemicals (i.e. strong oxidative bleaching agents)are used to prepare the washing bath.

Laser technology, such as CO₂ laser treatment, can be applied to textilematerials as an alternative to or along with conventional treatmentssuch as stone washing, sanding and bleaching for achieving the vintagelook. Laser treatments engrave the surface of the textiles, therebyobtaining colour fading to parts of the textile with high precision. Thelaser treatment is considered a dry treatment and therefore “green”.High temperature of laser burns and removes part of the surface of thetreated fabric, and thus colour removal is achieved. Textiles can bedamaged by the burn and removal of the treated surface, and deformationand loss in strength of the textiles may occur. Deformation of thetextile also limits the deep contrast look of a denim textile, i.e. thevisual difference in the laser engraved area on denim fabric (blue-whitecontrast). The operational parameters of the laser treatment thatprovide colour removal on the textile, e.g. laser energy and treatmenttime, are the same that may cause damages to the treated textile; forthis reason, it may be difficult to obtain a deep and intense vintagelook on a textile with laser treatments without damaging it.

There is the need to provide a process that overcomes the numerousdisadvantages of the finishing processes above mentioned to provide avintage look on textiles.

SUMMARY OF THE INVENTION

Aim of the present invention is a method for changing the colour of atextile to provide a vintage look that is not harmful to the environmentnor to the operating workers, that provides an effective colour fading,is fast, cost-effective, easy to carry out and that limits the eventualdamages to the treated textile.

The above-mentioned aim, as well as others, are reached through themethod of claim 1, namely a method for changing the colour of at least apart of a coloured fabric comprising the following steps:

-   -   a) providing said coloured fabric with one or more oxidizing        agents;    -   b) heating the fabric obtained according to step a); and    -   c) subjecting at least a part of the fabric obtained according        to step b) to a laser treatment;        wherein step b) comprises heating the fabric at a temperature        comprised in the range of 110° C. to 250° C.

The method of the invention provides a change in the colour of acoloured fabric, in particular provides a fading in colour, andtherefore vintage look is obtained. The method of the invention isadvantageous as it provides a vintage look to the fabric while avoidingor limiting the damages that conventionally occur when laser treatmentis carried out, e.g. the damages caused by the burn and removal of partof the surface of the fabric stated above. Indeed, according to themethod of the invention, the steps carried out before the lasertreatment step increases the colour fading effects provided by lasertreatment. Therefore, to achieve the same or even better colour fadingas in conventional laser treatments, the laser treatment of step c)according to the method of the invention can be carried out e.g. withless power and/or for less time. Accordingly, the laser treatment stepc) of the method of the invention provides cost-savings, in terms ofless energy and time required to provide colour fading, and at the sametime damages less the treated fabric with respect to conventional lasertreatments. The method of the invention is also easy and fast to carryout, as it requires conventional equipment and non-expensive chemicalsthat are commercially available.

The method of the invention does not harm the environment nor operatingworkers, as it employs non-harmful chemicals.

Other objects of the present invention are a fabric obtainable accordingto the method of the invention and a garment comprising such fabric.

The invention is now further disclosed more in detail according toembodiments thereof.

As used herein, “change in colour” or similar terms, unless otherwisespecified, refers to the fade of the colour of at least a part of acoloured fabric. This change in colour provides the vintage effect tothe fabric well known to the person skilled in the art.

The heating temperature of step b) has been found to be particularlyrelevant to provide the change in colour and therefore the vintage lookaccording to the method of the invention. The heating temperature hasalso been found not to damage the coloured fabric. According topreferred embodiments, the heating temperature is comprised in the rangeof 110° C. to 220° C., more preferably of 140° C. to 220° C., even morepreferably of 160° C. to 200° C., e.g. is 180° C. According toembodiments, step b) is carried out for a time of at least 20 seconds,preferably in the range of 20 seconds to 15 minutes, more preferably of30 seconds to 10 minutes, even more preferably of 30 seconds to 1.5minutes, for example of 45 seconds. This brief time period has beenfound suitable to provide a change in the colour of the treated fabricwhen the method of the invention is carried out and does not providedamages to fabric. Step b) aims to activate the oxidizing agents.Activation of the oxidizing agents enhances the effect provided by thelaser treatment in step c), i.e. the colour fading effect.

Without being bound to a specific technical explanation, we believe thatthe activated oxidizing agents may be able to partially oxidize the dyeon the coloured fabric, possibly providing a partial, minor colourfading. Activation of the oxidizing agents is obtained by the heatingstep b).

This activation enhances the effects of laser treatment step c) andallows a much better control of the vintage effect with respect toconventional laser methods. For example, when the oxidizing agent ismagnesium nitrate hexahydrate and when the fabric is coloured withindigo, the heating step b) provides activation of magnesium nitratehexahydrate, which is believed to at least partially convert to nitricacid. This activation occurs at about 110° C. or more, preferably atleast at 125-130° C. Indigo may be partially oxidized by nitric acid,which converts to NO and water. Preferred oxidizing agents are hydratednitrates, e.g. Mg dihydrate, Mg hexahydrate (Mg(NO₃)₂.6H₂O) and Alnonahydrate (Al(NO₃)₃.9H₂O).

This first reaction obtained by the step of heating the fabric having onits surfaces hydrate compounds as oxidizing agents at specifictemperatures and for reduced time (preferably for 30 seconds to 1.5minutes) allows a first minor colour fading of at least part of thetreated fabric. A major colour fading is obtained in laser treatmentstep c), and can also involve heating at least part of activatedmagnesium nitrate hexahydrate to convert it to NO₂, O₂ and MgO.

Major colour fading obtained in laser treatment step c) as referredherein means a treatment that provides the vintage look to the fabric,i.e. the final, deep colour fading of the selected areas of fabric thatare treated with laser, and does not necessarily mean theconversion/reaction of the total amount of oxidizing agents present onthe fabric. Step a) provides a coloured fabric to which one or moreoxidizing agents are applied to. In embodiments, the oxidizing agent canbe one or more of the following: perborate, persulfate, peroxide,permanganate, perchlorate, dichromate, chlorate, chlorite, bromate,nitrite, nitrate ions and/or salts containing the above ions. Morepreferably, the oxidizing agent is selected from nitrates, nitrate ionsand/or hydrated nitrate salts.

A preferred nitrate salt is magnesium nitrate. Magnesium nitrate, inparticular magnesium nitrate hexahydrate, has been found to beparticularly effective to provide the change of the colour to thecoloured fabric according to the method of the invention. Magnesiumnitrate is a salt that is commercially available and is not harmful tothe environment, to the operators and to the fabric itself. Preferredcompounds are hydrated nitrates, as for example magnesium nitratedihydrate (H₄MgN₂O₈), magnesium hexahydrate (Mg(NO₃)₂.6H₂O). In aparticularly preferred embodiment, the oxidizing agent is magnesiumhexahydrate. Other examples of suitable oxidizing agents can be zincnitrate, aluminium nitrate, sodium nitrate, silver nitrate, potassiumnitrate, strontium nitrate, sodium nitrite.

Still further oxidizing agents may be selected from at least one ofammonium persulfate, sodium persulfate, sodium perborate, sodiumperborate monohydrate, potassium dichromate, sodium dichromate, ammoniumdichromate, barium peroxide, hydrogen peroxide solutions, strontiumperoxide, zinc peroxide, sodium peroxide, calcium chlorate, potassiumchlorate, sodium chlorate, magnesium perchlorate, sodium perchlorate,sodium perchlorate monohydrate, ammonium perchlorate, sodium chlorite,calcium hypochlorite, potassium permanganate, sodium permanganate,ammonium permanganate, and potassium bromate.

The amount of oxidizing agents per square meter of fabric can depend onthe fabric to be treated. Preferably, the amount of oxidizing agents persquare meter of fabric is comprised in the range of 0.1 g/m² to 100g/m², more preferably of 1 g/m² to 50 g/m², even more preferably of 10g/m² to 30 g/m². It has been found that the amounts of oxidizing agentsindicated above provide an effective change in colour in the treatedfabric.

According to embodiments, the fabric with one or more of an oxidizingagent is obtained by applying a composition comprising said one or moreoxidizing agents to said fabric.

In particular, the fabric can be immersed in the composition, and/or thecomposition can be used to coat the fabric, whereby the oxidizing agentsare applied to the fabric. The fabric may be squeezed to provide therequired amount of oxidizing agent. According to preferred embodiments,a useful method to apply the composition comprising the oxidizing agentsto the coloured fabric is padding. The composition can also compriseother components, such as wetting agents, preferably non-ionic wettingagents.

The composition is preferably an aqueous composition. For example, saidaqueous composition may be advantageously used when the oxidizing agentis magnesium nitrate.

According to embodiments, the composition comprises an amount ofoxidizing agent comprised in the range of 40 g/L to 200 g/L, preferablyof 80 g/L to 160 g/L, more preferably is 120 g/L; and/or an amount ofwetting agent comprised in the range of 0.5 g/L to 20 g/L, preferably of1.5 g/L to 6 g/L, more preferably is 3 g/L. The composition applied tothe fabric according to the method of the invention does not comprise(i.e. it is free from) catalysts, such as acid or basic catalysts.Examples of these acid catalysts can be found in patent application US2018/0291553 A1 at paragraphs [0031] to [0033].

Advantageously, the composition does not damage the fabric, as thechemicals present in the said composition are not harmful to the fabric.

According to embodiments, the method of the invention further comprisesa drying step a′), said step a′) being carried out after step a) andbefore step b). The drying step a′) is preferably carried out at atemperature lower than the temperature of step b). Part of the oxidizingagents may also be activated during the drying step a′). The drying stepa′), as well as the heating step b), can be carried out by any suitablemeans, such as with an apparatus, e.g. a stenter, or air drying;advantageously, these two steps can be carried out in the sameapparatus, e.g. in the same stenter. According to embodiments, thedrying step a′) is carried out at a temperature comprised in the rangeof 80° C. to 220° C., preferably 110° C. to 190° C., more preferably is150° C., the temperature of step a′) being lower than the temperature ofstep b). Advantageously, the drying step can be carried out until thefabric reaches a relative humidity lower than 20%, preferably lower than15%, more preferably lower than 10%, even more preferably of about 6% orlower.

Preferably, step a′) and/or step b) are carried out by hot airtreatment, e.g. in a stenter or in a fan-assisted oven. According toembodiments, the laser treatment of step c) is carried out with a carbondioxide laser (CO₂ laser).

According to embodiments, the laser treatment of step c) is carried outwith a dpi value comprised in the range of 20 to 50, preferably of 33 to37.

According to embodiments, the laser treatment of step c) is carried outwith a focal length comprised in the range of 80 to 148 cm, preferablyis 148 cm.

According to embodiments, the laser treatment of step c) is carried outwith a laser beam frequency of 5 kHz.

According to embodiments, the laser treatment of step c) is carried outwith a pulsed laser. Preferably, the energy per pulse is comprised inthe range of 450 to 650 W, preferably is 450 W.

According to embodiments, the laser treatment of step c) is carried outwith a jump speed is about 5150 μm/s. As used herein, “jump speed”refers to the transition velocity of the laser beam from an engravingpoint to another.

According to embodiments, the laser treatment of step c) is carried outwith a jump delay comprised in the range of 50 to 300 μs, preferably isabout 50 μs. As used herein, “jump delay” refers to the preparation time(i.e. delay time) of the laser before engraving when it reaches anengraving point to another.

According to embodiments, step c) is carried out using one or more ofthe laser parameters (i.e. dpi, focal length, laser beam frequency,energy per pulse, jump speed and jump delay) as disclosed above.

Step c) can be carried out either on the warm fabric, for exampleimmediately after or shortly after step b) has been carried out, or onthe cold fabric after the fabric subjected to step b) has cooled down.

It has been found that laser treatment, for example the laser treatmentof step c), provides an improved colour fading when steps a) and b) arecarried out, compared to the colour fading obtained by the same lasertreatment without first carrying out steps a) and b). The heating of thefabric provided with nitrate ion and/or nitrate salts and/or suitableoxidizing agents according to the method of the invention has been foundto be particularly relevant to provide the above-mentioned increase incolour fading of the laser treatment. For this reason, as it isdemonstrated in the Experimental section below, the method of theinvention allows obtaining a suitable and effective change to the colourof the fabric by reducing the operational parameters of the lasertreatment that may cause damages to the fabric (such as laser treatmenttime). Laser treatment step c) provides major colour fading, whereby astrong and deep colour fading is obtained. Accordingly, vintage effectis obtained after step c) of the invention on the laser engravedarea(s).

The method of the invention allows a much better control of the vintagelook of the fabric compared to conventional methods that provide vintagelook, in particular to conventional laser treatments. The better controlis achieved by the combination of a first, minor bleaching with heat(step b)) and then a second, major bleaching with laser treatment (stepc)). It was advantageously observed that the combination of the dryingtreatment according to step a′) of the method of the invention and theheating treatment according to step b) produces a partial activation ofoxidizing agents on the fabric and, thus, a first fading, which issubsequently enhanced by a major fading given by laser treatment.

It was surprisingly found that the activation of the fabric havingoxidizing agents on its surface, for example hydrated nitrates, attemperatures from 110° C. to 250° C. for a preset period of timeconsents to avoid the use of an acid or basic catalyst, thereby reducingthe amount of resources needed to obtain a fade effect on at least partof the coloured fabric. Another advantage of the method of the inventionis the possibility to provide the fabric treated only with the first,minor bleaching (step b)) to the producer of the garments. The producercan then carry out the second, major bleaching, namely the lasertreatment, directly to the garment, based on the requirements of themarket and when necessary. The garment producer can also treat thefabric according a preferred pattern of fading as required by the finallook of the garment.

The method of the invention also provides energy savings and timesavings. The invention method is also suitable to treatment of elasticfabrics, e.g. fabrics comprising elastic yarns, preferably elastomericyarns, because the lower energy required for the laser beam results in adramatically less damaged elastic material present in the laser treatedelastic yarns. If the fabric to be treated with the method of theinvention is an elastic fabric that requires a heat setting treatment,i.e. a treatment to fix the fabric stretchability, the heat settingtreatment and the heat treatment of step b) can be carried outsimultaneously. In other words, the heat treatment of step b) can alsobe used as a heat setting treatment to fix the stretchability of theelastic fabric to be treated with the method of the invention. As statedabove, conventional laser treatments may damage the fabrics, as theyresult in removal of part of the treated surface, whereas the method ofthe invention limits such damages. With reference to FIG. 1, whichrepresents a pair of pants 10 showing vintage look in determined,selected areas 11, the amount of fabric surface removed by a laser withthe method of the invention may be assessed on a washed fabric, i.e. afabric from which the Mg Nitrate or other oxidizing agent has beenremoved. For example, the linear density of one or more yarns of thearea showing vintage look 11, and the linear density of one or moreyarns of the area not showing vintage look 12 may be measured andcompared. Such assessment can be made, alternatively or together withthe above, by measuring the weight per area of part of the fabric ofarea 11 and the weight per area of part of the fabric of area 12. Inpossible embodiments, when the method of the invention is carried out,the measured linear density of a yarn, and/or the measured weight perarea of the fabric, of the area 11 may be substantially the same or verysimilar to the ones measured for the area 12. Accordingly, the areashowing vintage look 11 of the garment 10 is not substantially damagedor is only slightly damaged by the method of the invention.

According to embodiments, the coloured fabric is coloured with at leastan indigoid dye. Indigoid dyes are a group of dyes well known in theart, including indigo, that can be reduced to dihydro derivatives (leucoform) and can resemble indigo in their structure. The method of theinvention has been found particularly effective when the coloured fabricis dyed with at least an indigoid dye, such as indigo, providing a deepvintage look to the fabric.

According to embodiments, the coloured fabric is made of cellulose-basedfibres and/or blends thereof, preferably is made of cotton fibers and/orblends thereof. The fabric may be elastic. These types of fabrics areused in the denim industry, wherein the vintage look is particularlysought. Moreover, the change in colour provided by the method of theinvention has been found particular effective on these types of fabrics.

According to embodiments, one or more further steps to provide vintagelook can be carried out after step c). Preferably, such further step(s)is a stone washing step d) carried out after step c). The stone washingstep d) is useful to enhance the colour fading effect provided by themethod of the invention. Stone washing carried out after steps a) to c)is less harmful to the environment with respect to when it is carriedout alone: the change in colour is already provided by steps a) to c)according to the method of the invention, therefore the stone washingstep d) can be carried out for less time and/or with less stones toreduce the harmful grit produced by the stones.

According to embodiments, the coloured fabric treated according to themethod of the invention is part of a garment or apparel. This allowsproviding the change in colour to targeted part(s)/area(s) of thegarment or apparel so that the final product, i.e. the garment orapparel, has the vintage look in the part(s)/area(s) where it is wanted.The method of the invention allows to control the part(s)/area(s) of thegarment where the change in colour has to occur, as the change in colourwill occur only in the part(s)/area(s) of the garment wherein steps a)to c) are carried out. According to embodiments, steps a), a′) (ifpresent) and b) can be carried out on the coloured fabric, and step c)can be carried out on the garment comprising such coloured fabric. Thisallows the advantage stated above, i.e. the possibility to provide thefabric treated only with the first, minor bleaching (step b)) to theproducer of the garments.

A further object of the present invention is a fabric obtainableaccording to the method as defined in any one of its embodiments. Thefabric of the invention shows a vintage look in its parts wherein themethod of the invention has been carried out and is not substantiallydamaged by the method of the invention, or its damages are reducedcompared to conventional laser treatment having the same depth/strengthof colour fading. Another object of the invention is a garmentcomprising the fabric of the invention according to any of itsembodiments.

Fabrics and garments of the invention have been treated with oxidizingagents and may comprise an amount of e.g. nitrate ions and/or of nitratesalts and/or of counter-ion(s) (when nitrate salts have been used asoxidizing agents) after the method of the invention has been carried outon them. According to a preferred embodiment, fabrics and garments ofthe invention may comprise an amount of e.g. nitrate ions and ofcounter-ion(s) (when hydrate nitrates have been used as oxidizingagents) after the method of the invention has been carried out on them.

Accordingly, the amount of oxidizing agents can be evaluated byseparating the oxidizing agents, e.g. nitrate ions and/or the nitratesalts and/or the counter-ion(s), from the fabric or garment of theinvention with known methods, and by quantifying such an amount withknown methods, e.g. complexometric titration or chromatography.

The amount of fabric surface removed in the fabrics or garments of theinvention may be assessed as disclosed above with reference to FIG. 1,preferably after the fabrics or garments have been washed such that theyare separated from the composition comprising the oxidizing agents, e.g.with the method stated above.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 represents a garment, in particular a pair of pants, showingvintage look in determined areas.

FIG. 2a is a picture of a comparative fabric which is subjected to lasertreatment only. FIG. 2b is a picture of a fabric of the invention.

FIG. 3a is a macro picture of a comparative fabric which is subjected tolaser treatment only. FIG. 3b is a macro picture of a fabric of theinvention.

EXPERIMENTAL SECTION AND DETAILED DESCRIPTION OF THE FIGURES

The invention is further illustrated by means of FIGS. 2a, 2b, 3a and 3bof examples that are provided for illustrative purposes only and do notaim to limit the scope of the invention.

Example 1

A composition comprising 120 g/L of magnesium nitrate hexahydrate and 3g/L of a nonionic wetting agent (Cottoclarin TR (BRP Kimya)) isprepared. An indigo coloured cotton fabric is padded with theso-prepared composition (step a)), thereby providing 22 g of magnesiumnitrate hexahydrate per square meter of indigo coloured cotton fabric.Then, the fabric is dried in a stenter machine at 150° C. until itreaches 6% of relative humidity (step a′)). Afterward, the fabric isheated in the same stenter at 180° C. for 45 seconds (step b)). Finally,a laser treatment step with a CO₂ laser (VAV r-Series 650 W) is carriedout on a predetermined area of the fabric (step c)). Laser parametersare 37 dpi, focal length: 148 cm, frequency: 5 kHz, energy per pulse:450 W, jump speed: 5149.7 μm/s and jump delay: 50 μs. The colour hasfaded in the area where laser treatment has been carried out, thereby avintage look is obtained.

To further improve the vintage look of the fabric, the fabric has beensubjected to stone washing for 30 minutes (step d)). The colour hasfaded on the whole fabric; the area where laser treatment has beencarried out presents a higher colour fading with respect to the otherareas.

Example 2

Comparative Example of Change in Colour

A fabric of the invention is prepared according to steps a), a′), b) andc) as disclosed in Example 1.

A comparative fabric is prepared by carrying out laser treatment usingthe same parameters disclosed in Example 1 starting from an identicalfabric as the one of Example 1. The comparative fabric has not beensubjected to steps a), a′) and b) of the method of the invention.

The change in colour of the fabrics is evaluated by Datacolor 6000spectrophotometer using the strength adjustment method, which is aconventional method for comparing the strength of colours. Maxabsorption peak is set at 660 nm. Fix adjustment strength is set to100%. The comparative fabric shows a result of 100% strength. The fabricof the invention shows a result of 52% strength. According to the aboveresults, the fabric of the invention has less colour strength comparedto the comparative fabric, therefore a higher colour fading is obtainedwith the method of the invention compared to the laser treatment only.The results of this example are also showed in FIGS. 2a and 2b , whichshow respectively the comparative fabric and the fabric of theinvention, and FIGS. 3a and 3b , which show respectively macro picturesof the comparative fabric and of the fabric of the invention. As it canbe observed by FIGS. 2 and 3, the change in colour is more apparent inthe fabric of the invention (FIGS. 2b and 3b ) with respect to thechange in colour in the comparative fabric (FIGS. 2a and 3a ).

Therefore, it has been demonstrated that carrying out steps a) and b) ofthe method of the invention before laser treatment improves the colourfading effects of the laser treatment itself.

Example 3

Energy and Time Saving of the Method of the Invention

A comparative fabric and a fabric of the invention have been preparedstarting from identical untreated fabrics. The comparative fabric hasbeen prepared carrying out only laser treatment on the untreated fabric.

It has been observed by the present Example that the laser treatment tomanufacture the fabric of the invention provided an energy saving ofabout 12% to 20% and a time saving of about 12% to 15% per garment, inparticular per pair of pants, and an energy saving of about 120 to 130 Wand of about 86 seconds per m² of treated fabric, with respect to thelaser treatment to manufacture the comparative fabric, to provide acomparable vintage look.

The present Example proves that the laser treatment (step c)) of themethod of the invention, compared to laser treatment only, (i) providescost-savings in terms of energy-savings and time-savings, and (ii) canbe carried out with reduced values of the operational parameters thatmay cause damages to the fabric, such as laser energy and lasertreatment time.

Example 4

The method of the invention is carried out on a fabric. 5 g of suchfabric are kept in 200 mL of deionized water for 30 minutes at atemperature of 50° C. Then, complexometric titration is carried out onthe water above using EDTA. It resulted that such water contained 5.8mg/L of magnesium ion corresponding to about 62 mg/L of magnesiumnitrate hexahydrate.

1. A method for changing the colour of at least a part of a colouredfabric comprising the following steps: a) providing said coloured fabricwith one or more of an oxidizing agent, preferably selected from:perborate, persulfate, peroxide, permanganate, perchlorate, dichromate,chlorate, chlorite, bromate, nitrite ions, nitrate ions and/or saltscontaining the above ions; b) heating the fabric obtained according tostep a); and c) subjecting at least a part of the fabric obtainedaccording to step b) to a laser treatment; wherein step b) comprisesheating said fabric at a temperature comprised in the range of 110° C.to 250° C.
 2. The method according to claim 1, wherein the heatingtemperature is comprised in the range of 110° C. to 220° C.
 3. Themethod according to claim 1, wherein the heating temperature iscomprised in the range of 160° C. to 200° C.
 4. The method according toclaim 1, wherein heating step b) is carried out for a time of at least20 seconds.
 5. The method according to claim 1, wherein said oxidizingagent is selected from nitrate ions and/or nitrate salts.
 6. The methodaccording to claim 1, wherein said oxidizing agent is selected fromhydrated nitrates.
 7. The method according to claim 1, wherein saidfabric with one or more of an oxidizing agent is obtained by applying acomposition comprising said one or more oxidizing agents to said fabric.8. The method according to claim 7, wherein said composition is anaqueous composition comprising an amount of said oxidizing agent in therange of 40 g/L to 200 g/L and/or an amount of wetting agent comprisedin the range of 0.5 g/L to 20 g/L.
 9. The method according to claim 1,further comprising a drying step a′), said step a′) being carried outafter step a) and before step b) and at a temperature comprised in therange of 80° C. to 220° C., the temperature of step a′) being lower thanthe temperature of step b).
 10. The method according to claim 1, whereinsaid laser treatment of step c) is carried out using one or more of thefollowing laser parameters: a dpi value comprised in the range of 20 to50; a focal length comprised in the range of 80 to 148 cm; a laser beamfrequency of 5 kHz; an energy per pulse comprised in the range of 450 to650 W; a jump speed is about 5150 μm/s; and a jump delay comprised inthe range of 50 to 300 μs.
 11. The method according to claim 1, whereinsaid coloured fabric is coloured with indigo and/or at least an indigoiddye.
 12. The method according to claim 1, wherein said coloured fabricincludes cellulose-based fibres.
 13. The method according to claim 1,wherein a stone washing step d) is carried out after step c).
 14. Themethod according to claim 1, wherein said coloured fabric is part of agarment or apparel.
 15. A fabric as obtainable according to steps a) andb) as defined in claim 1, said fabric comprising an oxidizing agent. 16.A fabric as obtainable according to the method of claim 1, comprisingelastic yarns.
 17. A garment comprising the fabric according to claim15.
 18. A method for increasing the colour fading of a laser treatmenton coloured fabrics, characterized in that steps a) and b) as defined inin claim 1 are carried out before said laser treatment in the absence ofacid catalysts.